1. Field of the Invention
This invention relates to a brake control valve for an automobile, and more particularly to a brake control valve suitable for starting the automobile stopped facing upwardly on an inclined roadways.
2. Description of the Prior Art
Generally when the driver or operator will start the automobile stopped by a side braking system or a hand braking system, facing upwardly on an inclined roadway, the driver treads an accelerator pedal to raise the rotational speed of the internal combustion engine to a certain extent, while the driver actuates a clutch pedal to softly press a clutch disc to a fly wheel in a clutch system. Such a condition of the clutch system is generally called "semi-clutching condition". Next, the driver further treads the accelerator pedal to gradually start the automobile, releasing the brake of the hand braking system and maintaining the semi-clutching condition.
As above described, when the automobile stopped on the inclined road-way will be started, the hand lever of the hand braking system, the clutch pedal and the accelerator pedal should be operated almost at the same time. Such operations are very difficult for the driver inexperienced in drive of the automobile. The inexperienced driver sometimes fails to start the automobile. At such a time, the automobile moves back to collide with another automobile in some cases.
Such a brake control valve to facilitate the start of the automobile stopped on the inclined roadway was proposed that includes a one-way valve which is closed by a movable valve member when the automobile is facing upwardly on the inclined roadway, to check brake fluid flow from a wheel cylinder to a master cylinder, and a cam shaft interconnected to a clutch pedal, having a cam portion positioned in a brake fluid passage. The brake control valve is arranged in a brake fluid conduit between the master cylinder and the wheel cylinder. The cam portion is displaced with actuation of the clutch pedal to displace the movable valve member to open and close the one-way valve.
When the automobile using the above described brake control valve will be stopped facing upwardly on the inclined roadway, the master cylinder is actuated to apply the brake fluid pressure to the wheel cylinder. The clutch pedal is operated to disengage the clutch disc from the fly wheel in the direction that the brake fluid pressure is maintained in the brake fluid conduit. Thus, the one-way valve is closed to check the brake fluid flow from the wheel cylinder to the master cylinder. Although the foot of the driver is removed from the brake pedal, the brake fluid pressure is held in the conduit between the one-way valve and the wheel cylinder. For the start of the automobile, the clutch pedal is operated to softly press the clutch disc to the fly wheel, namely to put the clutch system into the semi-clutching condition. The one-way valve is opened to release the brake fluid pressure held in the conduit. The accelerator pedal is treaded simultaneously with the clutch operation, to raise gradually the speed of the engine. The automobile is started without operation of the hand braking system.
In the above-described brake control valve, one end portion of the cam shift is positioned at the exterior of the body of the brake control valve, while another end portion of the cam shaft is positioned in the brake fluid passage within the interior of the body of the brake control valve. Accordingly, the brake fluid pressure is applied to the other end of the cam shaft to press the latter to the inner wall of the brake control valve. For that reason, a force required to drive the cam shaft must be sufficient to overcome the brake fluid pressure in addition to being sufficient to rotate the shaft. In some cases, there was the serious problem that the brake control valve was not operated by actuation of the clutch pedal.